My suggestion for this 'first notice' of male pattern baldness is to start on Nizoral shampoo. Use it 2-3 times a week.
It is an antifungal that helps the accelerative effect that fungal irritation has on the male pattern baldness cycle, and is also a mild anti-androgen. In effect, it packs a mild, two-pronged approach against male pattern baldness. Studies show it has a beneficial impact on hair equavalent to minoxidil 2%, without having to take minoxidil. It's a good starting point.
As for Nizoral 1% versus 2%, well, 2% normally requires a prescription in the US but is easily available online. Studies show that the additional 1% of Ketoanalconahole in the 2% does not add all that much extra bang on the margin, but if it is your only hairloss tool you are using you might consider it to be on the safe side. I think it's a tad more expensive after the shipping costs, but it is an option. Personally, I use 1% and it suits me just fine. Your call.
Keep in mind that hairloss is not a sudden event where you go from full head to horeshoe in a rapid rate. For me, I had very fast temple recession at age 19 or so, but it was mild and did not 'dig' into my hairline very much at all, and then it stopped for several years.
Maybe wait on Propecia until you see thinning or have itching/irritation in areas that are significantly deep into your cosmetically acceptable hairline. Keep in mind that once you start, you can't stop it and have to keep on taking it. If you can maintain an age-appropriate hairline despite the thinning you are facing now for a few more years, which was the case for me, taking Propecia now may be a bit premature.
I would NOT suggest minoxidil for you. It is not the right tool for your hairline and age, at this point. You have caught your male pattern baldness at a time when anti-androgens would be the best approach. minoxidil is a tool for people who have a pre-existing bald spot or bald temples and need to reinvogorate potential growth therein.